In the past year, our HLA typed donor file has been expanded and histocompatible platelets and granulocytes are now available for both therapeutic and prophylactic transfusions. Preliminary results of a prophylactic granulocyte trial indicate a decreased rate of infection in the granulocyte transfused group although the rate of alloimmunization may be increased. Autologous frozen platelets have become a major part of our support program and analysis of 91 transfusions to 25 leukemic patients demonstrates recoveries which are 67% of results with fresh platelets. Cell Collection studies have demonstrated that premedication with dexamethasone does not adversely affect in vivo and in vitro platelet function and that platelets collected with the Haemonetics Model 30 function and circulate normally. Gravity leukopheresis has been shown to be an efficient but slow method of granulocyte collection perhaps best suited to collection of blasts and leucocytes from patients with chronic myelogenous leukemia. An analysis of approximately 150 patients with acute nonlymphocytic leukemia did not reveal any association between HLA phenotype of haplotype and the occurrence of prognosis of the leukemia. Studies with indium labeled platelets and studies of granulocyte migration to skin chambers are in progress.